1. Field of the Invention
The invention relates a switch for changing the power source that supplies power via a fuse or relay to certain components or systems of a vehicle that require electrical power.
2. Description of the Related Art
Automotive vehicles continue to have increasingly complex arrays of components and systems that require electrical power to operate. The power may be derived, for example, from an on-board battery or alternator. The types of electronic components and systems vary considerably from one vehicle model to another for a particular automobile manufacturer, and also can vary from one vehicle to another within a particular model type depending upon the accessories that have been ordered by the purchaser. Changes to electronic components and systems in an automotive vehicle often will require a different arrangement of fuses and relays and may require connection to different power sources.
Automotive vehicles have power distribution boxes, auxiliary boxes or junction boxes for accommodating a large number of fuses and relays. For simplicity, these boxes will be referred to herein as junction boxes. The typical junction box has a housing molded from a synthetic resin. The typical junction box housing is likely to accommodate a plurality of busbars, circuit boards and/or terminal fittings. The junction box housing also is likely to have structures for clamping and/or routing cables and wires therein. Supply or input cables extend from the battery, alternator or other power source on the vehicle to the junction box housing and connect to busbars or terminal fittings in the junction box for supplying power. Output wires also extend from other busbars or terminal fittings in the junction box to the various components and systems of the vehicle that require power.
The junction box housing also is molded to define a plurality of sockets into which fuses and relays are replaceably mounted. In this regard, the typical fuse or relay has a housing formed from a nonconductive material. A power limiting means is embedded in the fuse or relay housing. Blade terminals connect to the power limiting means in the fuse or relay and project from the housing. The blade terminals project in a common direction and typically lie in a common plane. The typical fuse or relay has two parallel blades projecting from the housing. However, some fuses and relays have three parallel blades projecting from the housing and disposed in a common plane (e.g. a micro3 fuse). The fuse or relay is mounted into the appropriate socket of the junction box so that the blade terminals of the fuse or relay connect to terminal fittings or busbars in the junction box.
The fuses and relays are selected in accordance with the power limits of the corresponding electronic component to which the power will be supplied. Additionally, the power source to which the fuse or relay is connected depends upon the characteristics of the component or system to which the power will be supplied.
The automotive industry is highly competitive with respect to the cost charged to purchasers and with respect to the costs that will be charged by vendors and suppliers of the components that are incorporated into the vehicle. Even small savings in cost and minor improvements in efficiency can be commercially very advantageous.
The many different types of electronic components and systems often require different arrangements of fuses and relays and require the fuse or relay that is connected to a particular component or system to receive power from a different power source. Providing an entirely different junction box for each possible arrangement of the electronic components is economically infeasible. The junction box can be re-opened and the wiring therein can be changed to accommodate a need for a different power source. However, the interior of the junction box is extremely complex and varies considerably from one vehicle to another. As a result, rewiring mistakes are highly likely and can cause significant damage to the electrical system of the vehicle. Damage of this type can affect the way the vehicle will perform, and hence can be very dangerous. Furthermore, changes to the circuitry within a junction box are very time-consuming and therefore impose a significant cost penalty.
Junction boxes could be designed with extra sockets for fuses or relays or with sockets that can accommodate fuses or relays in different positions depending upon the required power source. For example, the inventor herein has considered a junction box with a linear array of three adjacent terminal fittings comprising: a middle terminal fitting connected to an output line and first and second end terminal fittings connected respectively to first and second input lines that deliver power from first and second power sources respectively. A fuse or relay could be connected to the middle terminal fitting and a first of the end terminal fittings for connection to a first power source or could be connected to the middle terminal fitting and the second of the end terminal fittings for connection to the second power source. However, this option creates the potential for inserting the fuse or relay into engagement with the wrong terminal fittings or busbars in the junction box, thereby providing connection to the wrong power source. Furthermore, a linear arrangement of three terminal fittings on a junction box could be misinterpreted as intended for the commercially available fuses with three parallel blade terminals. Connection of the fuse or relay to the wrong power source or incorrect connection of a three-blade fuse to two power sources could cause substantial damage to the circuitry within the junction box and to the component to which the power is supplied.
In view of the above, it is an object of the invention to provide a junction box with an ability to switch the power source for an electronic component or system of a vehicle while avoiding improper connection of fuses or relays to the optional power sources.